Implement unsafe Sync for global structs containing raw ptrs

Author: lucic71

cpp2rust/converter/converter.cpp

@@ -688,6 +688,7 @@ void Converter::EmitRustStructOrUnion(clang::RecordDecl *decl) {
   }
   AddDefaultTrait(decl);
   AddByteReprTrait(decl);
+  AddSyncTrait(decl);
 }
 
 bool Converter::VisitCXXRecordDecl(clang::CXXRecordDecl *decl) {
@@ -3457,6 +3458,26 @@ void Converter::AddDefaultTrait(const clang::RecordDecl *decl) {
 
 void Converter::AddByteReprTrait(const clang::RecordDecl *decl) {}
 
+static bool recordImplementsSync(const clang::RecordDecl *decl) {
+  for (auto field : decl->fields()) {
+    if (field->getType()->isPointerType()) {
+      return true;
+    }
+  }
+  return false;
+}
+
+void Converter::AddSyncTrait(const clang::RecordDecl *decl) {
+  if (!recordImplementsSync(decl)) {
+    return;
+  }
+
+  StrCat("\n// SAFETY: preserves unsafe C semantics; thread-safety is the "
+         "programmer's responsibility\n");
+  StrCat("unsafe impl Sync for", GetRecordName(decl));
+  PushBrace brace(*this);
+}
+
 void Converter::ConvertUnsignedArithBinaryOperator(clang::BinaryOperator *op,
                                                    clang::Expr *expr) {
   StrCat(token::kDot);

cpp2rust/converter/converter.h

@@ -466,6 +466,8 @@ class Converter : public clang::RecursiveASTVisitor<Converter> {
 
   virtual void AddByteReprTrait(const clang::RecordDecl *decl);
 
+  virtual void AddSyncTrait(const clang::RecordDecl *decl);
+
   virtual void
   ConvertUnsignedArithBinaryOperator(clang::BinaryOperator *binary_operator,
                                      clang::Expr *expr);

cpp2rust/converter/models/converter_refcount.cpp

@@ -503,6 +503,8 @@ void ConverterRefCount::AddByteReprTrait(const clang::RecordDecl *decl) {
   PushBrace brace(*this);
 }
 
+void ConverterRefCount::AddSyncTrait(const clang::RecordDecl *decl) {}
+
 std::string
 ConverterRefCount::GetSelfMaybeWithMut(const clang::CXXMethodDecl *decl) {
   return "&self";

cpp2rust/converter/models/converter_refcount.h

@@ -39,6 +39,8 @@ class ConverterRefCount final : public Converter {
 
   void AddByteReprTrait(const clang::RecordDecl *decl) override;
 
+  void AddSyncTrait(const clang::RecordDecl *decl) override;
+
   void AddDefaultTrait(const clang::RecordDecl *decl) override;
 
   void AddDefaultTraitForUnion(const clang::RecordDecl *decl) override;